The invention relates generally to methods of improving surface emitting lasers. More specifically, the invention relates to methods of assembling amplified vertical cavity surface emitting lasers (VCSELs) and the devices resulting therefrom.
Vertical cavity surface emitting lasers (VCSELs) are becoming an important component in electrical devices. VCSELs are becoming the component of choice for numerous applications, supplanting other types of lasers in a number of applications including data communication, optical interconnections and memory, sensors, printers, etc. The success of VCSELs is a direct result of the novel vertical geometry. The vertical geometry gives VCSELs a number of their advantageous operating characteristics, especially including significantly lower operating currents (to the mA range) and power dissipation/emission (to the mW/s) at Gbit data rates; high reliability ( greater than 107 Hrs MTTF), wafer-level batch fabrication and testing, and utilization of the existing LED (Light Emitting Diode) infrastructure; increased fiber coupling efficiency ( greater than 90%), and simplified drive electronics, all of which translate into a significant cost savings. VCSELs are also extremely useful because they emit power at a discrete wavelength; they have a single longitudinal mode, and can be made to have a single spatial mode.
Although VCSELs offer a number of significant advantages for their relatively low cost of production, they are not without their disadvantages. One of the disadvantages of VCSELs is their low single-mode power output. One solution to this problem is to make the diameter of the laser beam bigger. A larger laser would have a higher power output. However, when VCSELs are made larger, they no longer have a single spatial mode, but produce multiple spatial modes, each having different wavelength peaks. Therefore, for applications that require small focal spots or single mode fibers, it would be desirable to have a VCSEL with greater power output that still maintains its single spatial mode and high modulation bandwidth.
A number of references disclose methods of increasing power output of a VCSEL, including Jost, G. et al., SBMO/IEEE MTT-S IMOC ""99 Proceedings, p. 193 (1999); Vemukai, M. et al., IEEE Photonics Technology Letters, 10 (8) (1998); and Izhaky, N., IEEE Jrnl. Of Quantum Elecs. 33 (7) (1997). The apparatuses disclosed their function to produce a laser beam that has been amplified from its original power. However, because of the way that the beam was amplified the resulting laser beam is asymmetric.
Therefore, there exists a need for an amplified vertical cavity surface emitting laser that retains a single spatial mode, a high modulation bandwidth is symmetric. VCSELs with these characteristics would also be advantageous for use in two-dimensional arrays.
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention, and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
The invention provides both devices and methods of manufacture. In accordance with one aspect of the invention a device is provided with a first portion that emits light that has at least one quantum well, a spacer layer, and a second portion with an amplifying region with at least one quantum well, where the device is configured so that the spacer layer transmits the light beam emitted by the first portion and the amplifying region increases the intensity of the light beam. The spacer layer can be made of any material that is transmissive of the light emitted from the first portion, including semiconductor material, dielectric material, or a gap.
In accordance with another aspect of the invention, a method of manufacturing a vertical cavity surface emitting laser is provided having the steps of forming a first portion that emits light with at least one quantum well, forming a spacer layer made of a material that is transmissive of light emitted from the first portion, forming a second portion having at least one quantum well, where the second portion is positioned over the spacer layer and the spacer layer is positioned over the first portion. The device can be manufactured in a number of ways, including on one substrate by epitaxial growth, or on two different substrates that are later secured together with the spacer layer in between.
The novel features of the present invention will become apparent to those of skill in the art upon examination of the following detailed description of the invention or can be learned by practice of the present invention. It should be understood, however, that the detailed description of the invention and the specific examples presented, while indicating certain embodiments of the present invention, are provided for illustration purposes only because various changes and modifications within the scope of the invention will become apparent to those of skill in the art from the detailed description of the invention and claims that follow.